Probably you hadnt enough space on nuvi, or something went wrong
Update Mapupdater to the latest version.
Put your Garmin Device.xml in an 4 gb sd/Garmin folder, connect it to pc and run again Garmin Mapudater.
Then replace old files in nuvi, check Garmin Device.xml for files paths.
Voice commands dont work if you dont have the entire CNNAM-
[Only registered and activated users can see links. ]
Do you have bluetooth icon in menu? What do you have in device info? 3790 or 37xx ?